Sizing paper



Patented 'Oct. 20, 1936 Otto mess and Charles E. Johnson, Appleton, Wia,asslgnors to The Institute of Paper Chemistry, Appleton, Win, acorporation of Wiscon- Serial No. 3,307

No Drawing. Application January ca, 1935,

17 Claims. (Cl- 92-21) Our invention relates to the sizing of paper andrelates more particularly to sizing with paraflinand the like to producea paper which is suitable for writing, printing, and the like.

We are aware that paraflin has heretofore been suggested in connectionwith the sizing of paper and especially in admixture with rosin size.However, when such previously-known sizes are set through the use ofacidic material, such as alum. the particles of 'paramn tend to coalesceto form large aggregates which appear in the finished sheets astranslucent or semi-translucent "wax spots and which also offer troublein the papermaking operation by forming .parafiln spots on the wire,thus interfering with the operation of the paper machine. While thisdifficulty may be reduced by the use of very small quantities ofparail'in, such procedure eliminates the advantage of sizing withparafiin which may be obtained l when larger quantities arefused. Anobject of our invention is to devise a method & whereby large quantitiesof paraifin may be used for sizing while avoiding the disadvantagesabove referred to.

Another object of Tour invention is to provide, as a new composition ofmatter, a highly stable emulsion-of paraflin or thelike suitable .forsizing.

We have found that paraflin may be placed in a stable, finely-dividedform suitable for sizing by emulsifying it with an emulsifying agentsuch.

as a soluble soap, the emulsion being stabilized by a protein materialsuch as, for example, milk casein or soy bean casein; Such an emulsionis highly stable even though the parafiln may be present in quantitiesup to 75 per cent or more of the solids present in the mixture; theparaflin will not agglomerate upon heating or as a result 3 of thehydrolytic action of water, the action of alkaline-earth fillers, or anyother agents commonly used in paper making. x

. According to our invention, the emulsion is broken by addition of anacidic substance, such as alum, resulting in-i-setting the paraffin onthe fiber in finelydivided-form, each particle being surrounded by afilm of protein material.

- While we do not wish to limit ourselves to any particularitheory ofreaction, we believe that the protein which is present in the emulsion,when said emulsion is set by addition of acidic mateso rial, surroundsin a molecular film the minute particles of paraflln, thus preventingcoalescence thereof into larger particles. We have noted, also, thatamixture of parafiin emulsion and alkaline earth filler, wherein theemulsion has been broken by alum, does notshow the presence of aparailln film or of particles of parafiin which is visible to the nakedeye, even upon boiling and Y subsequent cooling. Our tests indicatethatthe paraflln is deposited on the fiber in sub-microscopic particlescoated with protein, whereby said 5 particles cannot agglomerate and arenot readily removable from the fiber.

Example This example is given as merely illustrative of 10 our inventionand not as limiting.

The following is a preferred way in which we prepare the parafllnemulsion. Ten parts by red oil, gums like gum arable, sodium stearate,

etc. To this mixtureAO parts of molten parafiin 20 are slowly run inunder agitation. The paraffin which we have been using represents normalparaflin of a melting point of 124 F. but higher melting point paraffinmight be used or lower melting point paraifin, even down to ordinaryoils. 25

The mixture of casein, emulsifier, and parailin is stirred with a highspeed stirrer or other suitable equipment. The time of mixing is usuallyapproximately 15 minutes, the mixture then being diluted with about 1000parts of water at ap- 30 proximately C. These temperatures can beadjusted, depending upon the melting point. of the paraflin used. Theemulsion can likewise be made through the use of a colloid mill or othersuitable equipment.

The preferred way in which this -'casein-parailin size is used is to addit to the pulp in the beaten and then set the size through the use ofalum in the usual manner to give an-aeidlty of from about pH 4.5 to-6.0. After about five minutes, which 40 will ordinarily be sufilcienttime for the setting of the size, the calcium carbonate or otheralkaline earth filler may beintroduced in slurry form at a concentrationof about two pounds per gallon, if such. filler is desired. The usualtreat- 5 ments which are given to pulp in the beater, such as coloringor the possible addition of starch, may also be practiced, if desired.In case it. is desired to use some rosin size in conjunction with thespecial casein-paraffin size, then both types of so a size may be addedto the pulp and set with alum in the usual manner.

In using the special casein-paraffin size along with an alkaline-earthfiller, in which case the whltewaters will be alkaline, the heatersshould 66 be made up with fresh water at the normal concentration ofbeater stock, say, from 4 to 6 per cent. However, the diluting water forthe dropping of the beaters may be white water if it is available, andthickened stock such as might be recovered from the usual white watersystems may be added just prior to dropping. In case no filler is usedor in case any fillers other than alkaline-earth fillers are used, suchas ordinary clay, no precautions need be taken with regard to the use ofwhite water, and it may be used to make up the beaters or may be omittedas desired. Wet and dry broke should be handled separately in a brokeheater and proportionately dropped to the beater chest, or it may beadded in slush form to the beater after the sizing operation.

A typical example for the production of book paper would be about asfollows:

Pounds Bleached soda pulp 500 Bleached sulphite pulp 500 To this pulp isadded about 5 per cent by dry weight of the casein-paraffin size, whichis then set with alum, as described. To this mixture may be added 300pounds of alkaline-earth filler, the whole beater having been made upwith fresh water but using any excess white water which may be availableduring the operation of dropping the beater.

The stock from the beater is handled in the usual manner over the papermachine. The mix will be on the alkaline side, in view of the excess ofalkaline earth filler, with a pH higher than 7.0, and the sizing in thefinished sheet will have been accomplished entirely through the use ofparamn in such a finely divided state that there will be no danger ofhaving parafiln spots in the finished paper or of operating troublesresulting from parailin spots on the wire of the paper machine.

It will be understood that other acid-reacting materials may be used toset the size, although alum is preferred. Also, while we have describedthe use of alkaline filler, it is understood that our invention is notrestricted to this featurevarious other types of filler may be used, ifdesired.

Various modifications and variations coming within the spirit of ourinvention will doubtless suggest themselves to those skilled in the art.Hence, we do not wish to be limited to the specific embodiments anddetails herein disclosed except to the extent indicated by the appendedclaims, which are to be interpreted as broadly as the state of the artwill permit.

The term casein as used in the claims includes both milk casein and soyabean casein.

We claim as our invention:

1. The method of sizing paper comprising introducing into a furnish anaqueous colloidal dispersion of waxy material stabilized with an acidprecipitable water-insoluble protein, the latter being present in such aquantity relative to the waxy material that particles thereof depositedon the paper fiber of the furnish are surrounded by a protein filmpreventing agglomeration of the waxy particles, and adding to thefurnish acidic material to precipitate the waxy and protein particles onthe fiber with the protein material coating the waxy particles.

2. The method of sizing paper comprising introducing into a furnish anaqueous colloidal dispersion of waxy material stabilized with an alkalisoluble water-insoluble protein precipitable from furnish acidicmaterial to precipitate the waxy and protein particles on the fiber withthe protein material coating the waxy particles.

'3. The method of sizing paper comprising introducing into a furnish anaqueous colloidal dispersion of waxy material stabilized with an acidprecipitable water-insoluble protein, the latter being present in such aquantity relative to the waxy material that particles thereof depositedon the paper fiber of the furnish are surrounded by a protein filmpreventing agglomeration of the waxy particles, and adding to thefurnish alum to precipitate the waxy and protein particles on the fiberwith the protein material coating the waxy particles.

4. The method of sizing paper comprising introducing into a furnish anaqueous colloidal dispersion of waxy material stabilized with an alkalisoluble water-insoluble protein precipitable from an alkali solution byan acidic material, said protein being present in such a quantityrelative to the waxy material that the particles thereof deposited onthe paper fiber of the furnish are surrounded by a protein filmpreventing agglomeration of the waxy particles, and adding to thefurnish alum to precipitate the waxy and protein particles on the fiberwith the protein material coating the waxy particles.

5. The method of sizing paper comprising introducing into a furnish anaqueous colloidal dispersion of waxy material stabilized with an acidprecipitable water-insoluble protein, the latter being present'in such aquantity relative to the waxy material that particles thereof depositedon the paper fiber of the furnish are surrounded by a protein filmpreventing agglomeration of the waxy particles, adding to the furnishacidic material to precipitate the waxy and protein particles on thefiber with the protein material coating the waxy particles, and thenadding to the furnish an alkaline earth filler.

6. The method of sizing paper comprising introducing into a furnish anaqueous colloidal dispersion of waxy material stabilized with an alkalisolublei water-insoluble protein precipitable from an alkali solution byan acidicmaterial, said protein being present in such a quantityrelative to the waxy material that the particles thereof deposited onthe paper fiber of the furnish are surrounded by a protein filmpreventing agglomeration of the waxy particles, adding to the furnishacidic material to precipitate the waxy and protein particles on thefiber with the protein material coating the waxy particles, and thenadding to the furnish an alkaline earth filler.

7. The method of sizing paper comprising introducing into a furnish anaqueous colloidal dispersion of waxy material stabilized with an acidprecipitable water-insoluble protein, the latter being present in such aquantity relative to the waxy material that particles thereof depositedon the paper fiber of the furnish are surrounded by a protein filmpreventing agglomeration of the waxy particles, adding to the furnishalum to precipitate the waxy and protein particles on the fiber with theprotein material coating the waxy particles, and then adding to thefurnish an alkaline earth filler.

' troducing into a furnish an aqueous colloidal ticles thereof ventinglatter .being present in such dispersion of waxy material, stabilizedwith an alkali soluble water-insoluble protein precipitable from alkali,solution by an acidic material, said protein being present in such aquantity relative to the waxy material that the pardeposited on thepaper fiber of the furnish are surrounded by a protein film pre-,agglomeration of the waxy adding to the iumish alum to precipitate thewaxy and protein particles on the fiber with the protein materialcoating the waxy particles, and

'15 then adding to the furnish an alkaline earth filler.

9. The method of sizing paper comprisingproviding a furnish havingpresent an aqueous colloidal dispersion of a mixture of rosin size andwaxy material, the latterbeing stabilized: with an acid precipitablewater-insoluble protein, the a quantity relativeto, the waxy materialthat particles thereofdeposited on the paper fiber of the furnish aresurrounded by a protein film, preventing agglomeration of the waxyparticles, and adding to the furnish acidic material to precipitate thewaxy and protein particles on the fiber with the protein materialcoating the waxy particles.

10. The method of sizing-paper comprising providing a furnish havingpresent an aqueous colloidal dispersion of, a mixture of rosin size andwaxy material, the latter being stabilized with an alkali solublewater-insoluble protein precipitable from an alkali solution by anacidic material, said protein being present in such a quantity relativetothe waxy material that particles thereof "deposited on the paper fiberof the i 'urnish are surrounded by a protein film preventingagglomeration of the waxy. particles, and adding to the furnish acidicmaterial to precipitate the waxy and protein particles on the fiber withthe protein material coating the waxy particles.

o tein, the 'latter being present 11. m method or sizing aper comprisingproviding a furnish having present and waxy material, the latter beingstabilized withan acid precipitable water-insoluble prorelative to thewaxy material that particles thereof deposited on the paper nish aresurrounded by a protein film preventing agglomeration of the waxyparticles, and adding to the furnish alum to precipitate the waxy andprotein particles on the fiber with the'protein material coating thewaxy particles.

12. The method of sizing paper comprising providing a furnish havingpresent an aqueous colloidal dispersion of a mixture of rosin size andwaxy material, ,the latter'being stabilized with a an alkali solublewater-insoluble protein precipitable from an alkali solution by anacidic material, said protein being present in such a quan-.

tity relative to the waxy material that particles thereof deposited onthe paper fiber of the furnish are surrounded by a ing agglomeration ofthe waxy particles,and adding to the furnish alum to precipitate thewaxy and protein particles on the fiber with the protein materialcoating the waxy. particles.

13. The method of sizing papercomprising provlding a furnish havingpresent an aqueous colparticles,

particles on the an aqueous. colloidal dispersion of a mixture of rosinsize in such a quantity fiber of the fur-' tein selected from proteinfilm preventvlding a furnish having present an aqueous colloidaldispersion of a mixture of rosin size and waxy'material t-he latterbeing stabilized with an alkali soluble water-insoluble proteinprecipitable from an alkali solution by an acidic material, said proteinbeing present in such a quantity relative to the waxy material thatparticles there of deposited on the paper fiber of the furnish 14. Themethod of sizing paper comprising proare surrounded by a protein filmpreventing agglomeration of the waxy particles, adding to the furnishacidic material to precipitate the waxy and protein particles on thefiber with the protein material coating the waxy particles, and

adding to the so-treated'furnish an alkaline earth '15. The method ofsizing paper comprising provlding a furnish having present an aqueouscolloidal dispersion waxy material, the latter being stabilized with anacid precipitable water-insoluble protein, the latter being present insuch. aquantity relative to the waxy material that particles thereofdeposited on the paper fiber of the furnish are surrounded by "a proteinfilm preventing agglomeration of the waxy particles, adding to thefurnish alum to precipitate the waxy'andprotein fiber with the proteinmaterial coating the waxy particles, and adding to the sotreated furnishan alkaline earth filler.

, 16. The method of sizing paper comprising pro-- vlding a furnishhaving p resent an' aqueous colloidal dispersion of a mixture of rosinsize and waxy material, the latter being stabilized with an alkalisoluble water-insoluble protein precipitable from an alkali solution byan acidic material, said protein being present in such a quantityrelative to the waxy material that particles thereof deposited on thepaper fiber of the furnish are surrounded by a protein film preventingagglom eration of the waxy particles, adding to the furnish alum toprecipitate the waxy and protein particles in the fiber with the proteinmaterial coating the waxy particles, so-treated furnish an alkalineearth filler.

17. The method 01" sizing paper comprising inof a. mixture. of rosinsize and and adding to'the troducing into aiurnish an aqueous colloidaldiswaxy material stabilized with a prothe group consisting of milkcasein, said protein being persion of a casein and soya bean present insuch aquantity relative to the waxy material-that particles thereofdeposited on-the -paper fiber. of the'furnish is surrounded by a proteinfilm' preventing agglomeration of the waxy particles, and adding to thefurnish acidic material to precipitate the wax and protein particlesonthe fiber with the protein material coating the waxy particles.

' O'I'IO KRESS.

CHARLES E. J OHNSDN.

